In a power transmission system for automobiles and various industrial machines, for example, in a drive shaft for front-wheel drive vehicles and for rear-wheel drive vehicles of an independent suspension type, as means for transmitting a rotational force at a constant velocity from an engine of the automobile to a wheel, there have been used a fixed type constant velocity universal joint which allows only angular displacement and a plunging type constant velocity universal joint which allows both angular displacement and axial displacement.
The drive shaft described above includes a propeller shaft for transmitting a rotational driving force from a transmission to a differential and a half shaft for transmitting a rotational driving force from the differential to a wheel. Further, a Birfield type constant velocity universal joint (BJ) is well-known as the fixed type constant velocity universal joint, and a double offset type constant velocity universal joint (DOJ) is well-known as the plunging type constant velocity universal joint.
For example, the fixed type constant velocity universal joint of the BJ type includes, as main components, an outer joint member having an inner spherical surface provided with a plurality of track grooves extending in an axial direction, an inner joint member having an outer spherical surface provided with track grooves extending in the axial direction in pairs with the track grooves of the outer joint member, a plurality of balls interposed between the track grooves of the outer joint member and the track grooves of the inner joint member so as to transmit torque, and a cage interposed between the inner spherical surface of the outer joint member and the outer spherical surface of the inner joint member so as to hold the balls. The plurality of balls are respectively housed in pockets formed in the cage and equiangularly arranged.
The outer joint member and the inner joint member in the fixed type constant velocity universal joint are generally manufactured by the following procedure. First, a columnar billet is roughly formed into a shape of the outer joint member or the inner joint member by hot forging, warm forging, or cold forging, and then lathing is performed on an outer spherical surface, an inner spherical surface, and an end surface of this raw material. After that, heat treatment is performed, and then the outer spherical surface, the inner spherical surface, and the track grooves are finished by grinding, quenched-steel trimming, or the like. In this manner, the outer joint member and the inner joint member are manufactured.
When an inner component including the inner joint member together with the balls and the cage is incorporated into the outer joint member, the outer joint member and the inner joint member manufactured as described above are selectively combined with each other so that PCD gaps and the like fall within a range of defined values.
In other words, as illustrated in FIG. 28, many outer joint members 210 and inner joint members 220 are ranked according to a PCD, and cages 240 having pocket widths in conformity with balls 230 are ranked according to the pocket widths.
From among the outer joint members 210, the inner joint members 220, the balls 230, and the cages 240 ranked into a plurality of ranks as described above, in consideration of combinations of components including the outer joint members 210, the inner joint members 220, the balls 230, and the cages 240 so that the PCD gaps and the like fall within the range of the defined values, and based on a matching table, the outer joint members 210, the inner joint members 220, the balls 230, and the cages 240 are selected and combined with each other (for example, refer to Patent Literatures 1 and 2).